Hysteria plays a certain role, inasmuch as when manifested during or after a paroxysm of intermittent fever, it may give rise to difficulties in diagnosis.

Neurasthenic disturbances have been observed in persons run down by frequent attacks (TriantaphyHides, loc. cit.). Sleeplessness is frequent both during and after the infection.

The rare febris vertiginosa may also be mentioned. This is characterized by a very severe vertigo at the time of the paroxysm. Triantaphyllides describes a special syndrome, occurring usually in old malarial patients, in which vertigo is the principal symptom. The vertigo is frequently very severe, and sometimes brings the patient to the ground. Periumbilical pains, dyspnea, palpitation, subsultus tendinum, vasomotor disturbances, pseudo asthma, and angina pectoris occur as associated symptoms in the syndrome. In all cases a hysterogenic spot has been found near the umbilicus.

Psychoses have been repeatedly observed, both accompanying the attack and as sequelae (Sydenham, Frerichs, Griesinger, Lemoine and Chaumier, von Krafft-Ebing, Pasmanik, Manson, and others).

Von Krafft-Ebing saw a remarkable case which manifested typical paroxysms of intermittent fever until, after a blow on the head, when an intermittent psychosis under the syndrome of epileptic confusion set in. Quinin and arsenic brought about recovery.

Manson's case is likewise very instructive. This was a man who came from Bombay to London and was placed in an insane asylum on account of symptoms of insanity. The blood examination showed the presence of malaria , and specific treatment was followed by cure.

Segard reports several cases of psychic disturbances. In one, acute mania with erotic outbreaks lasting three days after a malarial coma of fifty two hours' duration. In another, a patient in the hospital already on the road to recovery, though still manifesting fever, was struck with a fixed idea that he was needed at the fort. Otherwise the man behaved very reasonably. In spite of strict watch he succeeded in getting to the window and throwing himself into the sea. A third, in which a patient (who previously had several ordinary paroxysms), one evening during a paroxysm was seized with hallucinations, rushed out and wandered around in the thicket the whole night. Next morning he returned to the station in an extremely exhausted condition. The same evening a similar though milder paroxysm with hallucinations occurred.

Pasmanik seems to have had the widest experience with malarial psychoses. Among 5412 malarial cases he found mental disturbances 106 times.

A hereditary influence was present in none of these cases, and alcoholism in only 4.8 per cent. All were conditions of depression. Their duration varied between four days and three months, except one of persistent dementia. Pasmanik found comatose soporose conditions to be the most common in children. On exacerbations of chronic malaria melancholia arose, and in cachectics, simple melancholic and stuporous conditions. The worst prognosis was given by the delirium of cachectics, the result of a relapse.